Thermal processing apparatus, thermal processing method, and storage medium

ABSTRACT

When a substrate is transferred by a holding arm to a multiple tier wafer boat, contact between the holding arm and the substrate is prevented. When the wafer boat is not subjected to a thermal effect, a normal height position of a ring member is obtained by relatively elevating and lowering a transfer base member with respect to the wafer boat. Before a wafer, which is not yet thermally processed, is transferred to the wafer boat, a height position of the corresponding ring member is obtained. By comparing a difference between the normal height position of the ring member and the height position of the ring member before the wafer is transported, with a threshold value, whether to transfer the wafer by the wafer transfer mechanism to the wafer boat can be judged.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2008-222708 filed on Aug. 29,2008, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a technique for delivering substratessuch as semiconductor wafers by a substrate transfer means to and from asubstrate holder, in a vertical thermal processing apparatus thatthermally processes substrates held by the substrate holder in atier-like manner.

BACKGROUND ART

One of semiconductor manufacturing apparatuses, there is a verticalthermal processing apparatus that thermally processes a number ofsemiconductor wafers (hereinafter referred to as “wafers”) in block(batch). As shown in FIG. 11, for example, the vertical thermalprocessing apparatus includes a charge/discharge area through which acarrier, not shown, accommodating a plurality of wafers is carried toand from the outside. The wafers in the carrier are transferred by atransfer apparatus 11 to a wafer boat 12 capable of holding a number ofwafers 1 in a tier-like manner. By loading the wafer boat 12 to athermal processing furnace, not shown, a predetermined thermal processis simultaneously performed to the wafers 1.

The transfer apparatus 11 includes: a base table 13 capable of beingelevated and lowered, being rotated about a substantially vertical axis,and of being substantially horizontally moved; and forks 14 for holdinga plurality of, e.g., five wafers 1, the forks 14 being capable of beingmoved along the base table 13. For example, five wafers 1 can betransferred and transferred in batch by, e.g., the five forks 14 betweenthe carrier and the wafer boat 12. As shown in FIGS. 11 and 12, forexample, the wafer boat 12 has: a plurality of columns 15; a number ofholding parts 16 (see, FIG. 12) formed in the columns 15 for holdingperipheral portions of wafers, which are spaced at predeterminedintervals therebetween in the up and down direction; and ring members 17interposed between the holding portions 16 adjacent to each other in theup and down direction.

In the carrier, wafers are also held with their peripheral portions bynot-shown holding parts, with predetermined intervals between the wafersadjacent to each other in the up and down direction. As shown in FIG.12( a), the wafers 1 are received from the carrier and the wafer boat 12in the following manner. At first, the respective five forks 14 areinserted to spaces below the wafers 1 held by the carrier or the waferboat 12, and the forks 14 are elevated so as to float up the wafers 1.Then, the wafers 1 are received by the respective forks 14 and the forks14 are retracted, whereby the wafers 1 are received from the carrier orthe wafer boat 12. Thereafter, the wafers 1 are transferred by thetransfer apparatus 11 to an object to which the wafers 1 are to betransferred.

In the wafer boat 12, there is a demand for holding wafers 1 as many aspossible in order to improve a throughput of a process, and thus pitchesbetween the wafers 1 arranged in the wafer boat 12 tend to be narrowed.In particular, in the wafer boat 12 of a type in which the ring members17 are interposed between the wafers 1 adjacent to each other in the upand down direction, there is a case in which a pitch interval betweenthe wafers 1 is smaller than 10 mm. Since the wafers 1 and the ringmember 17 are arranged in this narrow space, when the fork 14 is movedinto (or retracted from) the space between the wafer 1 and the ringmember 17, a clearance between the fork 14 and the ring member 17 in theup and down direction is smaller than 1 mm. On the other hand, althoughthe wafer boat is generally made of quartz, when a process temperatureexceeds, e.g., 1000° C., the wafer boat 12 is deformed by the thermaleffect, so that the clearance may differ from the clearance uponteaching. The following reasons are considered for this deformation.Namely, since a succeeding process is started before the thermallyexpanded wafer boat 12 is not sufficiently cooled, the wafer boat 12 issubjected again to a thermal effect without the deformed wafer boat 12returning to the original state. In addition, since the ring member 17is larger than the wafer, the ring member 17 is vulnerable to thethermal effect, and is likely to be lowered by its own weight from a setposition. As the number of the process increases, the degree of thedeformation becomes serious because of these reasons.

Suppose that the clearance differs from the clearance upon teaching. Asshown in FIG. 12( b), when the wafer 1 is transferred by the fork 14,there is a possibility that the wafer 1 and the fork 14 might come intocontact with each other so that the surface of the wafer 1 might getscratched, and that the wafer 1 and the fork 14 might come into contactwith each other so that the transfer of the wafer 1 cannot be performed.

Citation 1 describes a vertical thermal processing apparatus including asubstrate holder capable of holding a plurality of objects to beprocessed in a tier-like manner in the up and down direction, and atransfer mechanism that transfers objects to be processed to thesubstrate holder, wherein information as to a feedback position, avelocity, and a current of a motor for driving the transfer mechanismare monitored, while the information and a preset information as to thenormal driving state of the motor are compared to each other. Upondetection of an abnormality, the driving of the transfer mechanism isstopped. However, this technique is a countermeasure taken when thedriving of the transfer mechanism become abnormal, and is not acountermeasure when the substrate holder becomes abnormal. Thus, thistechnique cannot solve the problem of the present invention.

-   [Patent Document 1] JP2007-251088A

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the above circumstances.The object of the present invention is to provide a technique forpreventing, when substrates are delivered by a substrate transfer meansto and from a substrate holder capable of holding a plurality ofsubstrates in a tier-like manner, a contact between a holding arm and asubstrate and a contact between the holding arm and the substrateholder.

The present invention is a vertical thermal processing apparatuscomprising: a thermal processing furnace; a substrate holder configuredto be carried into the thermal processing furnace and to hold asubstrate; a substrate transfer means including a holding arm configuredto hold a substrate and a transfer base member configured to support theholding arm; a height-position detecting part disposed on the substratetransfer means, the height-position detecting part being configured todetect a height position of the substrate transfer means with respect tothe substrate holder; a driving part controlled based on the heightposition detected by the height-position detecting part, the drivingpart being configured to relatively elevate and lower the substratetransfer means with respect to the substrate holder; a specific-portiondetecting part disposed on the substrate transfer means, thespecific-portion detecting part being configured to detect, when thesubstrate transfer means is relatively elevated and lowered with respectto the substrate holder, a substrate placed on each step of thesubstrate holder or a specific portion of the substrate holder, thespecific portion having a specific relationship with respect to eachsubstrate; a means configured to read the height position detected bythe height-position detecting part, when the specific-portion detectingpart detects the substrate or the specific portion; and a control partconfigured to control the substrate transfer means; wherein the controlpart includes: a difference detecting means configured to calculate adifference between a normal height position of each substrate or anormal height position of each specific portion, which height positionis obtained by relatively elevating and lowering the substrate transfermeans with respect to the substrate holder under the condition that thesubstrate holder is not subjected to a thermal effect, and a heightposition of each corresponding substrate or a height position of eachcorresponding specific portion, which height position is obtained byrelatively elevating and lowering the substrate transfer means withrespect to the substrate holder at a time of the operation of thevertical thermal processing apparatus; a judging means configured tocompare the difference and a threshold value and to judge whether thetransfer operation of the substrate from or to the substrate holder canbe performed or not based on the comparison result; and a meansconfigured to forbid the transfer operation of the substrate by thesubstrate transfer means, when the judging means judges that thetransfer operation of the substrate can not be performed.

The present invention is the vertical thermal processing apparatuswherein: the substrate transfer means is structured to be capable ofswitching from a single transfer mode of one substrate by the oneholding arm to a simultaneous transfer mode of a plurality of substratesby the plurality of holding arms; and the judging means compares thedifference with a first threshold value and with a second thresholdvalue that is larger than the first threshold value, and the judgingmeans judges that the transfer operation of the substrates by theplurality of holding arms can be performed when the difference is lessthan the first threshold value; the judging means judges that thetransfer operation of the substrate by the one holding arm can beperformed when the difference is not less than the first threshold valuebut less than the second threshold value; or the judging means judgesthat the transfer operation of the substrate from or to the substrateholder can not be performed when the difference is not less than thesecond threshold value.

The present invention is the vertical thermal processing apparatuswherein the specific-portion detecting part is formed of a mappingsensor including a light-emitting part and a light-receiving part fordetecting presence of the plurality of substrates placed on each step ofthe substrate holder.

The present invention is the vertical thermal processing apparatuswherein the substrate holder includes a ring member interposed betweenthe substrates placed in the substrate holder, the substrates beingadjacent to each other in an up and down direction, and the specificportion corresponds to the ring member.

The present invention is the vertical thermal processing apparatuswherein the time of the operation of the vertical thermal processingapparatus corresponds to a timing before a thermally processed substrateis taken out from the substrate holder.

The present invention is the vertical processing apparatus wherein thetime of the operation of the vertical processing apparatus correspondsto a timing after a thermally processed substrate have been alreadytaken out from the substrate holder and before a substrate to bethermally processed subsequently is not yet transferred to the substrateholder.

The present invention is a vertical thermal processing apparatuscomprising: a thermal processing furnace; a substrate holder configuredto be carried into the thermal processing furnace and to hold asubstrate; a substrate transfer means including a holding arm configuredto hold a substrate and a transfer base member configured to support theholding arm; a height-position detecting part disposed on the substratetransfer means, the height-position detecting part being configured todetect a height position of the substrate transfer means with respect tothe substrate holder; a driving part controlled based on the heightposition detected by the height-position detecting part, the drivingpart being configured to relatively elevate and lower the substratetransfer means with respect to the substrate holder; a specific-portiondetecting part disposed on the substrate transfer means, thespecific-portion detecting part being configured to detect, when thesubstrate transfer means is relatively elevated and lowered with respectto the substrate holder, a substrate placed on each step of thesubstrate holder or a specific portion of the substrate holder, thespecific portion having a specific relationship with respect to eachsubstrate; a means configured to read the height position detected bythe height-position detecting part, when the specific-portion detectingpart detects the substrate or the specific portion; and a control partconfigured to control the substrate transfer means; wherein the controlpart includes: a difference detecting means configured to calculate adifference between a normal distance between each substrate and asubstrate adjacent to the substrate or a normal distance between eachspecific portion and a specific portion adjacent to the specificportion, which distance is obtained by relatively elevating and loweringthe substrate transfer means with respect to the substrate holder underthe condition that the substrate holder is not subjected to a thermaleffect, and a distance between each corresponding substrate and thesubstrate adjacent to the substrate or a distance between eachcorresponding specific portion and the specific portion adjacent to thespecific portion, which distance is obtained by relatively elevating andlowering the substrate transfer means with respect to the substrateholder at a time of the operation of the vertical thermal processingapparatus; a judging means configured to compare the difference and athreshold value and to judge whether the transfer operation of thesubstrate from or to the substrate holder can be performed or not basedon the comparison result; and a means configured to forbid the transferoperation of the substrate by the substrate transfer means, when thejudging means judges that the transfer operation of the substrate cannot be performed.

The present invention is a thermal processing method performed by avertical thermal processing apparatus comprising a thermal processingfurnace, a substrate holder configured to be carried into the thermalprocessing furnace and to hold a substrate, and a substrate transfermeans including a holding arm configured to hold a substrate and atransfer base member configured to support the holding arm, the verticalthermal processing apparatus being configured to thermally process thesubstrate; the thermal processing method comprising: obtaining, as anormal height position, a height position of the substrate placed oneach step of the substrate holder or a height position of a specificportion of the substrate holder, the specific portion having a specificrelationship with respect to each substrate, under the condition thatthe substrate holder is not subjected to a thermal effect; obtaining, aheight position of each corresponding substrate or a height position ofeach corresponding specific portion, at a time of the operation of thevertical thermal processing apparatus; calculating a difference betweenthe normal height position of each substrate or the normal heightposition of each specific portion, and the height position of eachsubstrate or the height position of each specific part, the heightposition being obtained at the time of the operation of the verticalthermal processing apparatus; comparing the difference with a thresholdvalue and judging whether the transfer operation of the substrate fromor to the substrate holder can be performed or not based on thecomparison result; and forbidding the transfer operation of thesubstrate by the substrate transfer means when it is judged that thetransfer operation of the substrate can not be performed.

The present invention is the thermal processing method wherein: thesubstrate transfer means is capable of switching from a single transfermode of one substrate by the one holding arm to a simultaneous transfermode of a plurality of substrates by the plurality of holding arms; inthe judging, the difference is compared with a first threshold value andwith a second threshold value that is larger than the first thresholdvalue, and the transfer operation of the substrates by the plurality ofholding arms can be performed when the difference is less than the firstthreshold value, the transfer operation of the substrate by the oneholding arm can be performed when the difference is not less than thefirst threshold value but less than the second threshold value, and thetransfer operation of the substrate from or to the substrate holder cannot be performed when the difference is not less than the secondthreshold value.

The present invention is a thermal processing method performed by avertical thermal processing apparatus comprising a thermal processingfurnace, a substrate holder configured to be carried into the thermalprocessing furnace and to hold a substrate, and a substrate transfermeans including a holding arm configured to hold a substrate and atransfer base member configured to support the holding arm, the verticalthermal processing apparatus being configured to thermally process thesubstrate; the thermal processing method comprising: obtaining, as anormal height position, a height position of the substrate placed oneach step of the substrate holder or a height position of a specificportion of the substrate holder, the specific portion having a specificrelationship with respect to each substrate, under the condition thatthe substrate holder is not subjected to a thermal effect; obtaining aheight position of each corresponding substrate or a height position ofeach corresponding specific portion at a time of the operation of thevertical thermal processing apparatus; calculating a difference betweenthe normal distance between each substrate and a substrate adjacent tothe substrate or a normal distance between each specific portion and aspecific portion adjacent to the specific portion, and a distancebetween each corresponding substrate and the substrate adjacent theretoor a distance between each corresponding specific portion and thespecific portion adjacent to the specific portion, the distance beingobtained at the time of the operation of the vertical thermal processingapparatus; comparing the difference with a threshold value and judgingwhether the transfer operation of the substrate from or to the substrateholder can be performed or not based on the comparison result; andforbidding the transfer operation of the substrate by the substratetransfer means when it is judged that the transfer operation of thesubstrate can not be performed.

The present invention is a storage medium storing a computer programexecutable by a computer to implement a thermal processing methodperformed by a thermal processing apparatus comprising a thermalprocessing furnace, a substrate holder configured to be carried into thethermal processing furnace and to hold a substrate, and a substratetransfer means including a holding arm configured to hold a substrateand a transfer base member configured to support the holding arm, thevertical thermal processing apparatus being configured to thermallyprocess the substrate; the thermal processing method comprising:obtaining, as a normal height position, a height position of thesubstrate placed on each step of the substrate holder or a heightposition of a specific portion of the substrate holder, the specificportion having a specific relationship with respect to each substrate,under the condition that the substrate holder is not subjected to athermal effect; obtaining, a height position of each correspondingsubstrate or a height position of each corresponding specific portion,at a time of the operation of the vertical thermal processing apparatus;calculating a difference between the normal height position of eachsubstrate or the normal height position of each specific portion, andthe height position of each substrate or the height position of eachspecific part, the height position being obtained at the time of theoperation of the vertical thermal processing apparatus; comparing thedifference with a threshold value and judging whether the transferoperation of the substrate from or to the substrate holder can beperformed or not based on the comparison result; and forbidding thetransfer operation of the substrate by the substrate transfer means whenit is judged that the transfer operation of the substrate can not beperformed.

The present invention is a storage medium storing a computer programexecutable by a computer to implement a thermal processing methodperformed by a thermal processing apparatus comprising a thermalprocessing furnace, a substrate holder configured to be carried into thethermal processing furnace and to hold a substrate, and a substratetransfer means including a holding arm configured to hold a substrateand a transfer base member configured to support the holding arm, thevertical thermal processing apparatus being configured to thermallyprocess the substrate; the thermal processing method comprising:obtaining, as a normal height position, a height position of thesubstrate placed on each step of the substrate holder or a heightposition of a specific portion of the substrate holder, the specificportion having a specific relationship with respect to each substrate,under the condition that the substrate holder is not subjected to athermal effect; obtaining a height position of each correspondingsubstrate or a height position of each corresponding specific portion ata time of the operation of the vertical thermal processing apparatus;calculating a difference between the normal distance between eachsubstrate and a substrate adjacent to the substrate or a normal distancebetween each specific portion and a specific portion adjacent to thespecific portion, and a distance between each corresponding substrateand the substrate adjacent thereto or a distance between eachcorresponding specific portion and the specific portion adjacent to thespecific portion, the distance being obtained at the time of theoperation of the vertical thermal processing apparatus; comparing thedifference with a threshold value and judging whether the transferoperation of the substrate from or to the substrate holder can beperformed or not based on the comparison result; and forbidding thetransfer operation of the substrate by the substrate transfer means whenit is judged that the transfer operation of the substrate can not beperformed.

According to the present invention, at the time of the operation of thevertical thermal processing apparatus, a difference between the heightposition of the specific portion of the substrate holder, the specificportion having a specific relationship with respect to the substrate,and the normal height position of the specific portion is calculated. Bycomparing the difference and the threshold value, whether to deliver thesubstrate by the substrate transfer means to the substrate holder isperformed or not is judged. When it is judged that the transferoperation of the substrate can not be performed, the transfer operationof the substrate by the substrate transfer means is forbidden. Thus,when the substrate is transferred to the substrate holder by the holdingarm disposed on the substrate transfer means, a contact between theholding arm and the substrate and a contact between the holding arm andthe substrate holder can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing an embodiment of a thermal processingapparatus according to the present invention.

FIG. 2 is a plan view showing the thermal processing apparatus.

FIG. 3 is a schematic perspective view showing a wafer transfermechanism, a carrier, and a wafer boat disposed on the thermalprocessing apparatus.

FIG. 4 is a side view of the wafer transfer mechanism and the waferboat.

FIGS. 5( a) and 5(b) are a plan view and a side view showing the wafertransfer mechanism.

FIG. 6 is s structural view showing the wafer transfer mechanism and acontrol part.

FIG. 7 is a flowchart for explaining an inspection of the wafer boat.

FIG. 8 is a characteristic view showing obtained data 1 of heightpositions of ring members in the wafer boat.

FIG. 9 is a characteristic view showing obtained data 2 of the heightpositions of the ring members in the wafer boat.

FIG. 10 is a characteristic view showing obtained data 3 of the heightpositions of the ring members in the wafer boat.

FIG. 11 is a schematic perspective view showing a conventional transferapparatus and a wafer boat.

FIGS. 12( a) and 12(b) are side views showing the conventional transferapparatus and the wafer boat.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a vertical thermal processing apparatus of the presentinvention is described herebelow. FIG. 1 is a longitudinal sectionalview showing an inside of the vertical thermal processing apparatus, andFIG. 2 is a schematic plan view thereof. In the drawings, the referencenumber 2 depicts a housing defining an external body of the apparatus.In the housing 2, there are disposed a charge/discharge area S1 throughwhich a carrier C serving as a container containing wafers W assubstrates, is carried into the apparatus and carried out therefrom, anda loading area S2 as a transport area (transfer area) through which thewafers in the carrier C are transferred and loaded into thebelow-described thermal processing furnace. The charge/discharge area S1and the loading area S2 are separated from each other by a partitionwall 21. The charge/discharge area S1 is filled with an atmospheric air,and the loading area S2 is filled with an inert gas atmosphere, such asnitrogen (N₂) gas atmosphere, or a clean and dry gas atmosphere (a gascontaining less particles and organic components, and having a dewpointnot more than −60° C.).

The charge/discharge area S1 is composed of a first area 22 that islocated on a front side when viewed from the front side of theapparatus, and a second area 23 located on a rear side. The first area22 is provided with a first table 24 on which a plurality of, e.g., twocarriers can be placed. As the carrier C, there is used a carrier Ccapable of accommodating therein a plurality of, e.g., twenty five300-mm wafers as substrates that are arranged in a tier-like manner withpredetermined intervals therebetween. The carrier C is made of a resin,for example, and can be sealed by closing a not-shown opening in thefront surface by a lid member. A second table 25 is disposed in thesecond area 23 of the charge/discharge area S1. On an upper part of thesecond area 23, there are disposed a carrier storage part 26 in whichthe carrier C can be stored, and a carrier transfer mechanism 27 thattransfers the carrier C between the first table 24, the second table 25,and the carrier storage part 26. The carrier transfer mechanism 27includes: an elevating and lowering part 27 a capable of being elevatedand lowered and having a guide rail extending in the right and leftdirection; a moving part 27 b capable of being moved in the right andleft direction while being guided by the guide rail; and two arms 27disposed on the moving part 27 b, the arms 27 being capable ofhorizontally transferring the carrier C by holding a flange part 20 onan upper surface of the carrier C by means of a holding part 27 d.

The partition wall 21 is provided with an opening 20 that communicatesthe inside of the carrier C and the loading area S2 when the carrier Cplaced on the second table 25 is brought into contact with the partitionwall 21. On the side of the loading area S2, the partition wall 21 has adoor 28 that opens and closes the opening 20, and a lid opening/closingmechanism 29 that opens and closes the lid member of the carrier C whilethe door 28 is being closed. After the lid member of the carrier C isopened, the door 28 is configured to be retracted upward or downward,for example, by a not-shown door opening/closing mechanism, such thatthe lid opening/closing mechanism 29 and the lid member do not interferewith the transfer of the wafers W. An inert-gas supply pipe (not shown)is disposed on an edge side of the opening 20 of the partition wall 21,and an exhaust channel (not shown) is disposed on a lower end side ofthe opening 20. These inert-gas supply pipe and the exhaust channelconstitute a gas replacing means that supplies an inert gas such as anitrogen gas into the carrier C with its lid member being opened so asto replace an inside air of the carrier C with the inert gas.

The vertical thermal processing apparatus of the present inventionincludes a thermal processing furnace 31, a wafer boat 3, and a wafertransfer mechanism 4, which are described herebelow.

Namely, the loading area S2 is equipped with the vertical thermalprocessing furnace 31 having a lower end thereof being opened as afurnace opening. Below the thermal processing furnace 31, the wafer boat3, which is a substrate holder for holding a number of wafers W in atier-like manner with predetermined intervals therebetween, is placed ona cap 32. The cap 32 is supported by an elevating and lowering mechanism33. The wafer boat 3 can be carried into and out of the thermalprocessing furnace 31 by the elevating and lowering mechanism 33. Thewafer transfer mechanism 4 as a substrate transfer means is disposedbetween the wafer boat 3 and the opening 20 of the partition wall 21.Wafers can be transferred by the wafer transfer mechanism 4 between thewafer boat 3 and the carrier C placed on the second table 25.

As shown in FIGS. 3 and 4, the wafer boat 3 includes a plurality ofcolumns 36 extending between a top plate 34 and a bottom plate 35. Thecolumns 36 has holding paws 37 on which peripheral portions of waferscan be placed. Ring members 38 are interposed between the holding pawls37 adjacent to each other in the up and down direction. The ring members38 are provided for improving an in-plane uniformity of a film thicknessof a film formed on each wafer W and an in-plane uniformity of a thermalprocess. The ring members 38 correspond to specific portions havingspecific relationships with respect to the wafers W in the wafer boat 3.Such a ring member 38 is made of, e.g., quartz. As shown in FIG. 4, anoutside diameter L1 and an inside diameter L2 of the ring member 38 areset such that the peripheral region of the wafer W and the ring member38 are overlapped with each other, when the wafer W and the ring member38 disposed therebelow are viewed in a plan view. An arrangementinterval between the holding pawls 37 adjacent to each other in the upand down direction is set at about 10 mm, and an arrangement intervalbetween the ring members 38 adjacent to each other in the up and downdirection is set at about 10 mm.

The wafer transfer mechanism 4 includes a plurality of, e.g., five forks41 (41 a to 41 e) each of which is formed of a holding arm for holding awafer W, and a transfer base member 5 that supports the forks 41 a to 41e so as to be movable forward and rearward. The transfer base member 5is rotated about the vertical axis by a rotational mechanism 51 formedof a motor M1, is elevated and lowered by an elevating and loweringmechanism 52, and is moved in the right and left direction along a guiderail 53 (see, FIG. 2) extending in the right and left direction alongthe arrangement direction of the carriers C. The elevating and loweringmechanism 52 is configured to rotate a not-shown elevation shaft, whichis disposed inside the guide rail 54 extending in the up and downdirection, by a motor M2 so as to elevate and lower the transfer basemember 5 along the guide rail 54, for example. The motor M2 is connectedto an encoder 55. The reference number 56 depicts a counter that countsthe pulse number of the encoder 55.

As shown in FIGS. 5( a) and 5(b), the forks 41 consist of the fiveforks, i.e., the first fork 41 a, the second fork 41 b, the third fork41 c, the fourth fork 41 d, and the fifth fork 41 d, each of which canhold a wafer W. When viewed in a plan view, each of the forks 41 a to 41e has two arm parts 42 a and 42 b extending in the forward and rearwarddirection with a predetermined space interposed therebetween. In each ofthe forks 41 a to 41 e, the peripheral portion of a wafer W can beplaced on two locations on a distal side of the arm parts 42 a and 42 bof the fork 41 and two locations on a proximal side thereof, i.e., theperipheral portion of the wafer can be placed on stepped parts 42 a, 43b, 43 c, and 43 d. Thus, the wafer W can be held such that the wafer isslightly floated upward from the fork 41. A proximal part of each fork41 is secured on a moving mechanism 45 via a holding member 44.

In this example, for example, the third fork 41 c can be independentlymoved forward and rearward along the transfer base member 5, and therest four forks 41 a, 41 b, 41 d, and 41 e, excluding the fork 41 c, canbe simultaneously moved forward and rearward. Namely, the transfer basemember 5 includes a first moving mechanism 45 a for moving forward thethird fork 41 c, and a second moving mechanism 45 b for simultaneouslymoving forward the four forks 41 a, 41 b, 41 d, and 41 e, excluding thethird fork 41 c. The moving mechanisms 45 a and 45 b can be respectivelymoved in the forward and rearward direction along the transfer basemember 5. That is to say, in the wafer transfer mechanism 4, there canbe performed both a single transfer in which one wafer W is transferredby an independent movement of the first moving mechanism 45 a, and abatch transfer in which a plurality of, e.g., five wafers aresimultaneously transferred by a cooperation of the first and the secondmoving mechanisms 45 a and 45 b.

An optical sensor 6 forming a specific-portion detecting part isprovided on the third fork 41 c. The optical sensor 6 is formed of alight-block type optical sensor, for example. A mapping sensor fordetecting presence of wafers W held on the wafer boat 3 can be used asthe optical sensor 6. The optical sensor 6 is fixed on the distal end ofthe third fork 41 c such that a horizontal optical axis L can be formed.For example, a light-emitting part 61 is fixed on an inner surface ofone of the arm parts 42 a and 42 b (in this example, on the innersurface of the arm part 42 a), and a light-receiving part 62 is fixed onan inner surface of the other of the arm parts 42 a and 42 b (in thisexample, on the inner surface of the arm part 42 b) at a position wherethe light axis L from the light-emitting part 61 is received. Thus, thelight-receiving part 62 is opposed to the light-emitting part 61.

A positional relationship between the third fork 41 c and the ringmember 38 is described with reference to FIG. 6. When the third fork 41c is located on an inspection position facing the ring member 38, andthe transfer base member 5 is relatively elevated and lowered withrespect to the wafer boat 3, the third fork 41 c is elevated and loweredso as not to interfere with the ring members 38, but the optical axis Lformed nearby the distal end of the fork 41 c by the optical sensor 6fixed on the third fork 41 c blocks a part of the respective ringmembers 38.

Thus, when the transfer base member 5 is relatively elevated and loweredwith respect to the wafer boat 3, the optical axis L is blocked by eachring member 38. That is to say, a timing at which the optical sensor 6detects data showing that a light ray is blocked is a timing at whichthe ring member 38 is detected. On the other hand, a height position ofthe transfer base member 5 is always monitored. When the optical sensor6 detects the light-block data, the height position of the transfer basemember 5 is read out. Then, a correspondence between the height positionof the transfer base member 5 and the height position of the ring member38 as the specific portion is determined. With the use of thecorrespondence, the height of the ring member 38 can be calculated. Inthis example, the height position of the transfer base member 5 is readout by counting the pulse number of the encoder 55 by the counter 56.Based on this, height position data of the respective ring members 38 inthe wafer boat 3 can be detected.

The encoder 55 corresponds to a height-position detecting part thatdetects a relative height position of the transfer base member 5relative to the wafer boat 3, the elevating and lowering mechanism 52corresponds to a driving part that is controlled based on the heightposition detected by the encoder 55, and the counter 56 corresponds to areading means that reads the height position detected by the encoder 55when the optical sensor 6 detects the ring member 38 as the specificportion. The detected values of the light-block data from the opticalsensor 6, the pulse numbers of the encoder 55 when the data aredetected, and the pulse values read by the counter 56 are outputted tothe below-described control part 7, and these values are calculated bythe control part 7 as the height position data of the respective ringmembers 38 in the wafer boat 3.

Next, the control part 7 is described with reference to FIG. 6. Thecontrol part 7 is incorporated in a computer, and includes a dataprocessing part formed of a program, a memory, and a CPU 71. The programincorporates instructions for implementing the below-described transferorder by sending control signals from the control part 7 to therespective elements of the thermal processing apparatus. A screen of thecomputer serves as a display means 81 through which a predeterminedsubstrate process and a predetermined inspection process can beselected, and parameters in the respective processes, a first thresholdvalue A, and a second threshold value B, which are described below, canbe inputted. In addition, the display means 81 can display thebelow-described inspection result. The program is stored in a storagepart such as a computer storage medium, e.g., a flexile disc, a compactdisc, a hard disc, an MO (magneto-optic disc), and is installed in thecontrol part 7.

In order to inspect the height positions of the ring members 38 of thewafer boat 3, the control part 7 includes an inspection program 72 ofthe wafer boat 3, a reference-data storage part 73, and obtained-datastorage part 74. The control part 7 can send predetermined controlsignals to the elevating and lowering mechanism 52 of the forks 41 a to41 e, the encoder 55, the counter 56, the optical sensor 6, the displaymeans 81 of the computer, and an alarm issuing means 82. Thereference-data storage part 73 is a means for storing height positiondata of the respective ring members 38 of the wafer boat 3, when theheight positions of the ring members 38 are normal. The obtained-datastorage means 74 is a means for storing height position data of therespective ring members 38 of the wafer boat 3 to be inspected.

The inspection program 72 includes a means 72 a for controlling thedrive of the wafer transfer mechanism 4 during inspection, a differencedetecting means 72 b, and a judging means 72 c for judging a manner of awafer W to be delivered by the wafer transfer mechanism 4 to the waferboat 3. The difference detecting means 72 b is a means for calculating adeviation that is a difference between the reference data stored in thereference-data storage part 73 and the obtained data stored in theobtained-data storage part 74. The judging means 72 c judges whether thetransfer operation of a wafer W can be performed by comparing thedifference (deviation) and the preset threshold values A and B, andoutputs a delivery command (transfer command) to the wafer transfermechanism 4 through the drive control means 72 a when a wafer W istransferred. On the other hand, when a wafer W can not be transferred,the judging means 72 c outputs a command for forbidding delivery(transfer operation) of a wafer W to the wafer transfer mechanism 4through a transfer forbidding means 72 d which is described below, andoutputs a command for displaying a predetermined alarm. Herein, todisplay an alarm means to turn on the alarm issuing means 82 such as alamp, to generate an alarm sound, and to display an alarm on the displaymeans 81 of the computer. The inspection program 72 includes thetransfer forbidding means 72 d that outputs a transfer forbiddingcommand to the wafer transfer mechanism 4 so as to control the wafertransfer mechanism 4, when the judging means 72 c judges that thetransfer operation of a wafer W can not be performed.

Next, a flow of wafers W in the above-described vertical thermalprocessing apparatus is described. Firstly, in the wafer boat 3, data asto the height positions of the respective ring members 38 of the waferboat 3 are previously obtained as normal reference data, before aprocess is performed, e.g., when the apparatus is set up and no thermaleffect is given to the wafer boat 3 (S1), and threshold values are setfor evaluating deviations (S2). As the threshold values, there are setthe first threshold value A which is a critical deviation at which abatch transfer of wafers by the five forks 41 a to 41 e can beperformed, and the second threshold value B which is a criticaldeviation at which the batch transfer by the five forks can not beperformed but a single transfer of a wafer by the single fork 41 c canbe performed. In this embodiment, the first threshold value A is set at1.00 mm, and the second threshold value B is set at 2.00 mm.

The reference data can be obtained as follows. For example, as shown inFIG. 4, the transfer base member 5 is moved to a position on which thethird fork 41 c is located below the lowermost ring member 38 b of thewafer boat 3, and the fork 41 c is moved up to the inspection position.As shown in FIGS. 4 and 6, the inspection position is a position atwhich, when the transfer base member 5 is elevated and lowered, the fork41 c does not interfere with the ring parts 38 but the optical axis L ofthe optical sensor 6 fixed on the distal end of the fork 41 c is blockedby the ring parts 38. Then, the transfer base member 5 is graduallyelevated up to a position at which the third fork 41 c is located abovethe uppermost ring member 38 a of the wafer boat 3. In this manner, atthe height positions where the ring members 38 are present, the opticalaxis L of the optical sensor 6 is blocked by the ring members 38,whereby light-block data are obtained. By reading the pulse numbers ofthe encoder 55 at these timings by the counter 56, the relative heightposition of the transfer base body 5 with respect to the wafer boat 3can be determined, and these data are obtained as the reference data ofthe height positions of the ring members 38.

Then, in the vertical thermal processing apparatus, the carrier C isplaced on the first table 24 by an automatic transfer robot, not shown,which is moved along a ceiling part of the clean room. Then, the carrierC is transferred to the second table 25 by the carrier transfermechanism 27, and the carrier C is hermetically brought into contactwith the opening 20 of the partition wall 21 by a not-shown mechanism.There is a case in which the carrier C is temporarily stored in thecarrier storage part 26, and is then transferred to the second table 25.

Thereafter, the lid member is removed from the carrier C by the lidopening/closing mechanism 29, and an inert gas such as a nitrogen gas isblown from the gas supply pipe, not shown, into the carrier C. Thus, thespace between the carrier C and the door 28 of the carrier C is filledwith the nitrogen gas. Subsequently, the door 28, the lidopening/closing mechanism 29, and the lid member are elevated, forexample, so as to be retracted from the opening 20, so that the insideof the carrier C and the loading area S2 are in communication with eachother.

On the other hand, in the wafer boat 3, before wafers W are transferred,e.g., at a timing when thermally processed wafers W are taken out fromthe wafer boat 3, and at a timing after thermally processed wafers Whave been already taken out from the wafer boat 3 and before wafers W tobe thermally processed subsequently are not yet transported to the waferboat 3, data as to the height positions of the respectivelycorresponding ring members 28 of the wafer boat 3 are obtained by thesame manner as the manner by which the reference data are obtained, andthe obtained data are stored in the obtained-data storage part 74 (S3).Then, the judging means calculates differences between the referencedata and the obtained data so as to obtain deviations, and compares thedeviations with the threshold values A and B so as to judge whether theheight positions of the ring members 38 are abnormal or not (S4).

The above method is concretely described with reference to the datashown in FIGS. 8 to 10. For example, when the deviations of all the ringmembers 38 are less than 1.00 mm, as shown in the obtained data 1 ofFIG. 8, since the deviations fall below the first threshold value A, theheight positions of the ring members 38 are judge to be normal. Thus, acommand is outputted to the wafer transfer mechanism 4 such that wafersare transferred by the general batch transport in which five wafers Ware transferred in batch by the five forks 41 a to 41 e (S5). At thistime, since wafers are generally transported in batch by the five forks41 a to 41 e, the deviations and the first and second threshold values Aand B are compared for each set of five ring members 38 from thelowermost ring member 38 b, for example. However, the comparison may beperformed for each set of five ring members 38 from the uppermost ringmember 38 a.

In view of the obtained data 2 shown in FIG. 9, deviations of the ringmembers 38 from the uppermost level to the 5th level are not less than1.00 mm but less than 2.00 mm. Namely, since the deviations exceed thefirst threshold value A but fall below the second threshold value B, acommand is outputted to the wafer transfer mechanism 4 such that thebatch transfer is switched from a simultaneous transfer mode in whichfive wafers W are transferred in batch by the five forks 41 a to 41 e,to the single transfer mode in which wafers are transferred one by oneby the single fork 41 c (step S6). In the ring members from the 6thlevel to the 10th level (step), only the deviation of the 6th ringmember is not less than the first threshold value A but less than thesecond threshold value B, and the deviations of the 7th to 10th ringmembers are less than the first threshold value A. Even when only one ofthe deviation of the ring member 38 among the set of five ring members38 is not less than the first threshold value A but less than the secondthreshold value B, a command is outputted to the wafer transfermechanism 4 such that the batch transport is switched to the singletransfer mode so as to transport wafers one by one (step S6). Since thedeviations of the 96th to 100th ring members 38 are less than the firstthreshold value A, a command is outputted to the wafer transfermechanism 4 such that the simultaneous transfer mode is performed by thefive forks 41 a to 41 e (step S5).

In the obtained data 3 shown in FIG. 10, when the deviations of all thering members 38 are not less than 2.00 mm, since the deviations exceedthe second threshold value B, the height positions of the ring members38 are judged to be abnormal, whereby a command is outputted to thewafer transfer mechanism 4 such that the transfer operation of wafers Wis forbidden, and a command is outputted to the display means 81 of thecomputer and the alarm issuing means 82 such that an alarm is displayed(S7). Then, a predetermined recovery operation and/or a predeterminedmaintenance operation is performed by an operator. Specifically, theheight positions of the ring members 38 of the wafer boat 3 are adjustedto the normal positions, and/or the ring member 38 is exchanged (S8).

When wafers W are transferred after data as to the height positions ofthe respective ring members 38 have been obtained in this manner, thewafers W in the carrier C are sequentially taken out therefrom by thefive forks or the single fork, and are transported to the wafer boat 3.When no wafer W remains in the carrier C and the carrier C becomesvacant, the aforementioned operations are reversely operated. Namely,the lid member of the carrier C is closed, the second table 25 is movedbackward so that the carrier C is separated from the partition wall 21,and the carrier C is transferred to the carrier storage part 26 wherethe carrier C is temporarily stored. After the predetermined number ofwafers W have been placed in the wafer boat 3, the wafer boat 3 iscarried into the thermal processing furnace 31, and the wafers W aresubjected to a thermal process such as a CVD process, an annealingprocess, and an oxidation process.

After the thermal process has been finished, data as to the heightpositions of the respectively corresponding ring members 38 in the waferboat 3 are obtained, in the same manner as the manner by which thereference data are obtained before the wafers W are transported, and theobtained data are stored in the obtained-data storage part 74. Then, thejudging means calculates differences between the reference data and theobtained data so as to obtain deviations. By comparing the deviationswith the threshold values, the judging means judges whether the heightpositions of the ring members 38 are abnormal or not. When thedeviations are less than the first threshold value A, it is judged to benormal, and a command is outputted such that the simultaneous transfermode (general batch transfer mode) is performed by the five forks. Whenthe deviations are not less than the first threshold value A but lessthan the second threshold value B, it is judged that the single transfermode can be performed so that the wafers are transferred one by one bythe single fork. When the deviations are not less than the secondthreshold value B, it is judged to be abnormal, and commands areoutputted such that the transfer operation of the wafers W is forbiddenand that the aforementioned alarm is outputted. During such a transferoperation of wafers, the wafers W in the wafer boat 3 are returned tothe carrier C in batch or one by one by the five forks or the singlefork of the wafer transfer mechanism 4. The reference data showing thenormal height positions of the ring members 38 of the wafer boat 3 canbe obtained when there is no thermal effect at all, for example, at atiming when the apparatus is set up, or after teaching duringmaintenance.

In such a vertical thermal processing apparatus, before wafers W whichare not yet subjected to a thermal process are transferred to the waferboat, and before wafers W which have been already subjected to a thermalprocess are received from the wafer boat 3, whether the height positionsof the ring members 38 of the wafer boat 3 are normal or not isinspected. When the deviations relative to the normal height positionsare not less than the second threshold value B, it is judged to beabnormal and the transfer operation of the wafers W by the wafertransfer mechanism 4 is not performed. In this case, after the heightpositions of the ring members 38 have been adjusted, the transferoperation is performed. Namely, since the transfer operation of thewafers W is not performed from or to the wafer boat 3 that undergoes asevere thermal deformation by a thermal effect, the contact between theforks 41 a to 41 e and the wafers W and the contact between the forks 41a to 41 e and the ring members 38 can be prevented from occurring.Therefore, the generation of scratches on the wafer W and generation ofparticles, which are caused by the contact, can be prevented, wherebyreduction in throughput of products can be restrained as well as thewafer boat 3 can be prevented from being damaged.

According to the use of this present invention, the inevitable troublebased on a change over time, i.e., the deformation of the wafer boat 3caused by a thermal effect can be prevented from occurring. In addition,since wafers W even with very small scratches and/or a small amount ofparticles cannot be shipped as products, the contact between the forks41 a to 41 a and wafers W can be prevented, in restraining reduction inthroughput.

Further, as described above, the contact between the forks 41 a to 41 eand wafers W and the contact between the forks 41 a to 41 e and the ringmembers 38 can be prevented from occurring. Thus, a significantlyimproved precision of the teaching operation to be previously performedis not required, whereby the structure of the apparatus and the programcan be simplified. In addition, as described above, the presentinvention can be regarded as an invention for checking a change overtime of the wafer boat 3 caused by a thermal effect. Thus, when thedifference between the normal reference data and the obtained databecomes large to some extent, the present invention can be utilized toknow the exchange timing of members such as the wafer boat 3 and thering members 38.

Furthermore, When the deviations between the height positions of thering members 38 of the wafer boat 3 and the normal height positionsthereof are not less than the first threshold value A but less than thesecond threshold value B, it is judged that the transfer operation bythe single fork can be performed and wafers are transferred one by one,although the batch transfer operation by the five forks is impossible.Thus, when the height positions of the ring members 38 are abnormal butthe degree thereof is negligible, the transfer operation of the wafers Wcan be continuously performed. Thus, it is not necessary to stop theapparatus for each time, whereby reduction in working efficiency of theapparatus can be prevented.

Moreover, the inspection as to whether the height positions of therespective ring members 38 are normal or not is performed as follows. Byproviding the optical sensor 6 on the third fork 41 c and relativelyelevating and lowering the transfer base member 5 with respect to thewafer boat 3, data relating to the respective ring members 38 areobtained by the optical sensor 6. Based on this, whether the heightpositions of the ring members 38 are judged to be normal or abnormal.Thus, the operation required for the inspection is simple, and theinspection can be performed with a high precision for a short period oftime. When the mapping sensor is utilized as the means for inspectingthe specific portion, it is not necessary to prepare a new sensor, whichis effective in terms of the structure of the apparatus and the cost.

In the present invention, it is possible to acquire accumulated data asto the height positions of the ring members 38 of the wafer boat 3,together with the parameters such as a temperature and a period of thethermal process and a cooling period of the wafer boat 3 after thethermal process, so as to estimate possible troubles based on theaccumulated data. Namely, based on a predetermined thermal processtemperature, a thermal process period, and a cooling period of the waferboat 3, the times of the process with the wafer boat 3, which invitesthe contact between the ring members 38 and wafers and the contactbetween the forks 41 and wafers, may be estimated and the result may bedisplayed.

Instead of the ring members 38, the specific portions detected by thespecific-portion detecting part may be the holding pawls by which wafersW can be held. Alternatively, when wafers W are directly held by groovesformed in the columns, the specific portions may be these grooves. Whenthe height positions of the holding pawls and the grooves are detectedby the optical sensor 6, the transfer base member 5 may be elevated andlowered such that the optical axis of the optical sensor 6 is blocked bythe wafers W held by the holding paws or the grooves, and the heightpositions of the holding pawls or the grooves may be detected based onthe light-block data. Further, it is possible to detect wafers W placedon the respective levels (steps) of the wafer boat 3 by thespecific-portion detecting part.

The specific-portion detecting part may be provided on the forks 41 a,41 b, 41 d, and 41 e, instead of the third fork 41 c, or may be providedone of the transfer base member 5 and the wafer transfer mechanism 4.Further, a reflection type optical sensor may be used as thespecific-portion detecting part.

In this case, a light ray from the light emitting part is reflected byperipheral surfaces of the ring members 38 and the wafers held by theholding pawls or grooves, whereby the height positions of the ringmembers 38 and the holding pawls or the grooves can be detected based ondata obtained when the reflected light is received by the lightreceiving part. Alternatively, a camera and a positional sensor, insteadof the optical sensor, may be used as the specific-portion detectingpart.

Further, the height-position detecting part may detect relative heightpositions of certain regions of the wafer transfer mechanism 4 such asthe forks 41 a to 41 e in addition to the transfer base body 5 withrespect to the wafer boat 3. Alternatively, the height-positiondetecting part may detect the relative height position of the wafertransfer mechanism 4 with respect to the wafer boat 3 by detecting arotational speed of the motor M2. Furthermore, a linear scale may beused as the height-position detecting part, and the scales of the linearscale may be read and counted by a reading means. In addition, when theheight positions of the specific portions are detected, not the wafertransfer mechanism 4 but the wafer boat 3 may be elevated and lowered.

Moreover, the present invention may be applied to a substrate transfermeans that performs only a batch transfer of wafers by means of aplurality of holding arms. In this case, one threshold value is set. Thesubstrate transfer means is controlled such that, when deviationsbetween the reference data and the obtained data are less than thethreshold value, the wafers are transferred in batch by the holdingarms, and that, when deviations exceed the threshold value, the transferoperation of the wafers W by the holding arms is forbidden. In addition,the present invention may be applied to a substrate transfer meanshaving only one holding arm.

In the above example, the difference detecting means 72 b of the controlpart 7 calculates a difference |An−Bn| in which An represents the heightposition of the n-th specific member (in this example, the ring member)of the wafer boat 3 in the normal condition and Bn represents the heightposition of the n-th specific member of the thermally processed waferboat 3, and compares the difference |An−Bn| with the threshold values.However, not limited thereto, the difference detecting means 72 b maycalculate a difference |(An−A(n−1))−(Bn−B(n−1)|, and the judging means72 c may evaluate a thermal deformation by comparing the difference withthe threshold values.

Namely, the difference detecting means 72 b of the control means 7 maycalculate a difference in distance between the n-th specific member inthe normal condition and the (n−1)th specific member adjacent thereto.

The invention claimed is:
 1. A vertical thermal processing apparatuscomprising: a thermal processing furnace; a substrate holder configuredto be carried into the thermal processing furnace and to hold asubstrate; a substrate transfer means including a holding arm configuredto hold a substrate and a transfer base member configured to support theholding arm; a height-position detecting part disposed on the substratetransfer means, the height-position detecting part being configured todetect a height position of the substrate transfer means with respect tothe substrate holder; a driving part controlled based on the heightposition detected by the height-position detecting part, the drivingpart being configured to relatively elevate and lower the substratetransfer means with respect to the substrate holder; a specific-portiondetecting part disposed on the substrate transfer means, thespecific-portion detecting part being configured to detect, when thesubstrate transfer means is relatively elevated and lowered with respectto the substrate holder, a substrate placed on each step of thesubstrate holder or a specific portion of the substrate holder, thespecific portion having a specific relationship with respect to eachsubstrate; a means configured to read the height position detected bythe height-position detecting part, when the specific-portion detectingpart detects the substrate or the specific portion; and a control partconfigured to control the substrate transfer means; wherein the controlpart includes: a difference detecting means configured to calculate adifference between a normal height position of each substrate or anormal height position of each specific portion, which height positionis obtained by relatively elevating and lowering the substrate transfermeans with respect to the substrate holder under the condition that thesubstrate holder is not subjected to a thermal effect, and a heightposition of each corresponding substrate or a height position of eachcorresponding specific portion, which height position is obtained byrelatively elevating and lowering the substrate transfer means withrespect to the substrate holder at a time of the operation of thevertical thermal processing apparatus; a judging means configured tocompare the difference and a threshold value and to judge whether thetransfer operation of the substrate from or to the substrate holder canbe performed or not based on the comparison result; and a meansconfigured to forbid the transfer operation of the substrate by thesubstrate transfer means, when the judging means judges that thetransfer operation of the substrate can not be performed.
 2. Thevertical thermal processing apparatus according to claim 1, wherein: thesubstrate transfer means is structured to be capable of switching from asingle transfer mode of one substrate by the one holding arm to asimultaneous transfer mode of a plurality of substrates by the pluralityof holding arms; and the judging means compares the difference with afirst threshold value and with a second threshold value that is largerthan the first threshold value, and the judging means judges that thetransfer operation of the substrates by the plurality of holding armscan be performed when the difference is less than the first thresholdvalue; the judging means judges that the transfer operation of thesubstrate by the one holding arm can be performed when the difference isnot less than the first threshold value but less than the secondthreshold value; or the judging means judges that the transfer operationof the substrate from or to the substrate holder can not be performedwhen the difference is not less than the second threshold value.
 3. Thevertical thermal processing apparatus according to claim 1, wherein thespecific-portion detecting part is formed of a mapping sensor includinga light-emitting part and a light-receiving part for detecting presenceof the plurality of substrates placed on each step of the substrateholder.
 4. The vertical thermal processing apparatus according to claim1, wherein the substrate holder includes a ring member interposedbetween the substrates placed in the substrate holder, the substratesbeing adjacent to each other in an up and down direction, and thespecific portion corresponds to the ring member.
 5. The vertical thermalprocessing apparatus according to claim 1, wherein the time of theoperation of the vertical thermal processing apparatus corresponds to atiming before a thermally processed substrate is taken out from thesubstrate holder.
 6. The vertical processing apparatus according toclaim 1, wherein the time of the operation of the vertical processingapparatus corresponds to a timing after a thermally processed substratehave been already taken out from the substrate holder and before asubstrate to be thermally processed subsequently is not yet transferredto the substrate holder.
 7. A vertical thermal processing apparatuscomprising: a thermal processing furnace; a substrate holder configuredto be carried into the thermal processing furnace and to hold asubstrate; a substrate transfer means including a holding arm configuredto hold a substrate and a transfer base member configured to support theholding arm; a height-position detecting part disposed on the substratetransfer means, the height-position detecting part being configured todetect a height position of the substrate transfer means with respect tothe substrate holder; a driving part controlled based on the heightposition detected by the height-position detecting part, the drivingpart being configured to relatively elevate and lower the substratetransfer means with respect to the substrate holder; a specific-portiondetecting part disposed on the substrate transfer means, thespecific-portion detecting part being configured to detect, when thesubstrate transfer means is relatively elevated and lowered with respectto the substrate holder, a substrate placed on each step of thesubstrate holder or a specific portion of the substrate holder, thespecific portion having a specific relationship with respect to eachsubstrate; a means configured to read the height position detected bythe height-position detecting part, when the specific-portion detectingpart detects the substrate or the specific portion; and a control partconfigured to control the substrate transfer means; wherein the controlpart includes: a difference detecting means configured to calculate adifference between a normal distance between each substrate and asubstrate adjacent to the substrate or a normal distance between eachspecific portion and a specific portion adjacent to the specificportion, which distance is obtained by relatively elevating and loweringthe substrate transfer means with respect to the substrate holder underthe condition that the substrate holder is not subjected to a thermaleffect, and a distance between each corresponding substrate and thesubstrate adjacent to the substrate or a distance between eachcorresponding specific portion and the specific portion adjacent to thespecific portion, which distance is obtained by relatively elevating andlowering the substrate transfer means with respect to the substrateholder at a time of the operation of the vertical thermal processingapparatus; a judging means configured to compare the difference and athreshold value and to judge whether the transfer operation of thesubstrate from or to the substrate holder can be performed or not basedon the comparison result; and a means configured to forbid the transferoperation of the substrate by the substrate transfer means, when thejudging means judges that the transfer operation of the substrate cannot be performed.